Threads, tasks, and synchronized learning notes (1). Synchronize learning notes

Threads, tasks, and synchronized learning notes (1). Synchronize learning notes

1. A simple way to create a thread is to define a delegate and call it asynchronously.

 1 using System; 2 using System.Threading; 3  4 delegate int WaitAWhileDelegate(int data, int ms); 5  6 class Program 7 { 8     static void Main(string[] args) 9     {10         WaitAWhileDelegate d = WaitAWhile;11         int data = 1;12         int ms = 3000;13         IAsyncResult a = d.BeginInvoke(data, ms, null, null);14         while (!a.IsCompleted)15         {16             Console.Write("*");17             Thread.Sleep(100);18         }19         int result = d.EndInvoke(a);20         Console.WriteLine("\nresult: {0}", result);21     }22 23     static int WaitAWhile(int data, int ms)24     {25         Console.WriteLine("WaitAWhile started.");26         Thread.Sleep(ms);27         Console.WriteLine("WaitAWhile completed.");28         return ++data;29     }30 }

Add the parameter value of the Sleep method of Line 1 in the Code. The number of asterisks output is reduced, and vice versa.

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2. IAsyncResult has an attribute named AsyncWaitHandle, which belongs to the WaitHandle class. The WaitOne method of this class will "take a timeout time as the first optional parameter, in which you can define the maximum waiting time ".

 1 using System; 2 using System.Threading; 3  4 class Program 5 { 6     delegate int WaitAWhileDelegate(int data, int ms); 7  8     static void Main(string[] args) 9     {10         WaitAWhileDelegate d = new WaitAWhileDelegate(WaitAWhile);11         int data = 1;12         int ms = 3000;13         IAsyncResult a = d.BeginInvoke(data, ms, null, null);14         while (true)15         {16             Console.Write("*");17             if (a.AsyncWaitHandle.WaitOne(50, false))18             {19                 Console.WriteLine("Can get the result now.");20                 break;21             }22         }23         int result = d.EndInvoke(a);24         Console.WriteLine("\nresult: {0}", result);25     }26 27     static int WaitAWhile(int data, int ms)28     {29         Console.WriteLine("WaitAWhile started.");30         Thread.Sleep(ms);31         Console.WriteLine("WaitAWhile completed.");32         return ++data;33     }34 }

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3. The third way to wait for the result is asynchronous callback. IAsyncResult also has an attribute named AsyncState. This attribute can be forcibly converted to its delegate.

 1 using System; 2 using System.Threading; 3  4 class Program 5 { 6     delegate int WaitAWhileDelegate(int data, int ms); 7  8     static void Main(string[] args) 9     {10         WaitAWhileDelegate d = new WaitAWhileDelegate(WaitAWhile);11         d.BeginInvoke(1, 1000, WaitAWhileComplete, d);12         for (int i = 0; i < 100; i++)13         {14             Console.Write("*");15             Thread.Sleep(50);16         }17     }18 19     static int WaitAWhile(int data, int ms)20     {21         Console.WriteLine("WaitAWhile started.");22         Thread.Sleep(ms);23         Console.WriteLine("WaitAWhile completed.");24         return ++data;25     }26 27     static void WaitAWhileComplete(IAsyncResult a)28     {29         if (a == null)30         {31             throw new ArgumentNullException("a");32         }33         WaitAWhileDelegate d = a.AsyncState as WaitAWhileDelegate;34         if (d == null)35         {36             throw new Exception("a.AsyncState can not convert to WaitAWhileDelegate");37         }38         int result = d.EndInvoke(a);39         Console.WriteLine("\nresult: {0}", result);40     }41 }

Note: The 11th parameter d in the BeginInvoke method of the 4th line Code cannot be null any more. Otherwise, the callback cannot be implemented, that is, the print output function of the 39th line in the WaitAWhileComplete function cannot be executed.

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4. Lamda expressions can be used instead of delegation.

 1 using System; 2 using System.Threading; 3  4 class Program 5 { 6     delegate int WaitAWhileDelegate(int data, int ms); 7  8     static void Main(string[] args) 9     {10         WaitAWhileDelegate d = new WaitAWhileDelegate(WaitAWhile);11         d.BeginInvoke(1, 1000, a => { int result = d.EndInvoke(a); Console.WriteLine("\nresult: {0}", result); }, d);12         for (int i = 0; i < 100; i++)13         {14             Console.Write("*");15             Thread.Sleep(50);16         }17     }18 19     static int WaitAWhile(int data, int ms)20     {21         Console.WriteLine("WaitAWhile started.");22         Thread.Sleep(ms);23         Console.WriteLine("WaitAWhile completed.");24         return ++data;25     }26 }

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